LOL re being the pushchair oracle lol
I have only quickly read this, but have you twigged that the lower seat of the Twone has 2 recline mechanisms - there is the zip, but the seat also tilts, so you have a choice of either recline or can use both to give a maximum recline. There's no doubt the Twone lower seat recline is better than the Oyster Max lower seat one.
With both pushchairs with a carrycot your baby would go underneath. However with the Oyster Max you can put a newborn in the upper seat parent facing. This does compromise on the space of the lower child though.
So with your eldest on top, there's plenty of space for your eldest in both seats. What I struggled with, was access to the Twone lower seat, but in carrycot mode this shouldnt be as much of an issue. But I couldnt even get my hands between the bars to wipe an upright child's nose, let alone posset from a laid down baby. I know parties didnt see it as an issue, but trying to get the lower child out in an emergency really is a bit of an ordeal as the top seat needs to be remove. The Max seats are much better for spacing and access. I like the footrests on both pushchairs for the lower child. There's loads and loads of photos on Best Buggy of children in both pushchairs along with reviews.
The Twone has the more compact fold really, however the Oyster chassis is quite open in the middle, so it depends how you put it into your car. The Oyster seats can be folded or open (I find its better to put one folded and one open or else they roll off each other) whereas the Twone seats nest - but one is a rigid L shape, which caused me a few issues.
The Max is great with a buggy board on.
I think putting them in your car would help you. But DO think through how you will get to the lower child in the Twone. Also look at basket space - the Max wins here - because you will need at least space for a raincover (huge thing on the Twone with no storage for it) or changing kit for the baby.